Problems In Quasi-Elastic Neutrino-Nucleus Scattering Gerry Garvey LANL, P-25 July 25,2011.
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Problems In Quasi-Elastic Neutrino-Nucleus Scattering Gerry Garvey LANL, P-25 July 25,2011
What is quasi-elastic scattering (QES)? Why has neutrino-nucleus QES Become Interesting? Inclusive Electron QES; formalism and results. (longitudinal and transverse, scaling) Extension to neutrino-nucleus QES processes. Differences between electron and neutrino QES experiments. Problems with impulse approximation. Possible remedies and further problems. Determining the neutrino flux?? Outline
QES is a model in which the results of elastic lepton- nucleon scattering (neutral or charge changing, (n p)) is applied to the scattering off the individual nucleons in the nucleus. The cross-section is calculated the square of the incoherent sum of the scattering amplitudes off the individual nucleons. Pauli exclusion is applied and a 3-momentum transfer q > 0.3GeV/c is required to resolve individual nucleons. What is Quasi-elastic Scattering?
Why has QES become Important? Research involving neutrino oscillations has required the extention of QES (CCQE) to neutrino-nucleus interactions. For 0.3<E ν < 3.0 GeV it is the dominant interaction. CCQE provides essential information for neutrino oscillations, neutrino flavor and energy. CCQE is treated as readily calculable, experimentally identifiable and allows assignment of the neutrino energy. Some 40 calculations published since 2005 Oscillation period: 1.27Δm ij 2 (ev 2 )× (L(km)/E ν (GeV)) Δm 23 2 =10 -3 L/E≈10 3 LBNE Δm 2S 2 =1 L/E≈1 SBNE
“ *** LSND effect rises from the dead… ?“ Long-Baseline News, May 2010:
New Subatomic Particle Could Help Explain the Mystery of Dark Matter. A flurry of evidence reveals that "sterile neutrinos" are not only real but common, and could be the stuff of dark matter. And it’s Getting Worse!! Cosmology, decay of sterile neutrino (dark matter), calibration of Ga solar neutrino detectors, increased flux from reactors HIDDEN CLUE: Pulsars, including one inside this "guitar nebula," provide evidence of sterile neutrinos.
C Ni Pb QES in NP originated in e-Nucleus Scattering Moniz et al PRL 1971 Simple Fermi Gas 2 parameter, S E, p F Impulse Approximation
Inclusive Electron Scattering Electron Beam Δ /E ~10 -3 Magnetic Spectograph Scattered electron Because the incident electron beam is precisely known and the scattered electron well measured, q and ω are precisely known without any reference to the nuclear final state
Quasi-Elastic Electron Scattering Single nucleon vector current
Scaling in Electron Quasi-elastic Scattering (1) The energy transferred by the electron (ω), to a single nucleon with initial Fermi momentum T N is the kinetic energy of the struck nucleon, E s the separation energy of the struck nucleon, E R the recoil kinetic energy of the nucleus. The scaling function F(y,q ) is formed from the measured cross section at 3- momentum transfer q, dividing out the incoherent single nucleon contributions at that three momentum transfer. Instead of presenting the data as a function of q and ω it can be expressed in terms of a single variable y.
Scaling in Electron Quasi-elastic Scattering (2) 3 He Raw dataScaled Excuses (reasons) for failure y > 0: meson exchange, pion production, tail of the delta.
Super Scaling The fact that the nuclear density is nearly constant for A ≥ 12 leads one to ask, can scaling results be applied from 1 nucleus to another? W.M. Alberico, et al Phys. Rev. C38, 1801(1988), T.W. Donnelly and I. Sick, Phys. Rev. C60, 065502 (1999) A new dimensionless scaling variable is employed Note linear scale: not bad for Serious divergence above
Separating Super Scaling into its Longitudinal and Transverse Responses Phys. Rev. C60, 065502 (1999) Longitudinal Transverse The responses are normalized so that in a Relativistic Fermi Gas Model: f L satisfies the expected Coulomb sum rule. ie. It has the expected value. f T has mostly excuses (tail of the Δ, meson exchange, pion production etc.) Fine for fixed q and different A. Note divergence below ψ’=0 Transverse Trouble even with the GOLD standard
Contrast of e-N with ν-N Experiments Electron Beam Δ /E ~10 -3 Magnetic Spectograph Scattered electron Neutrino Beam ΔE/ ~1 l - What’s ω ??? Don’t know E ν !!! What’s q ???? Very Different Situation from inclusive electron scattering!! Electron Neutrino-Mode Flux Neutrino
MiniBooNE: ν μ + 12 C CCQE Results PR D81 092005 (2010) Tabular results available in article M A =1.03 GeVM A =1.35 GeV Data-MC
While inclusive electron scattering and CCQE neutrino experiments are very different, the theory hardly changes. Neutrino (+), Anti-Neutrino(-) Nucleon CCQE Cross Section The f 1 and f 2 are isovector vector form factors that come from electron scattering. g 1 is the isovector axial form factor fixed by neutron beta decay with a dipole form, 1.27/(1+Q 2 /M A 2 ). M A =1.02±.02 Charged lepton mass=0
NUANCE Breakdown of the QE Contributions to the MB Yields
MiniBooNE Theory consensus What is Observed? CCQE
Some RPA p-h diagrams from Martini et al. PR C80, 065501 External interaction nucleon nucleon - hole delta virtual SRI π,ρ, contact Particle lines crossed by are put on shell Exchange Current and pionic correlation diagrams in Amaro et al. PR C82 044601 Exchange Correlation Diagrams of Some Short Range Correlations
Further Reaction Amaro et al; Phys. Lett. B696 151(2011). arXiv:1010.1708 [nucl-th] Included Meson Exchange into their SuperScaling (L) Approach Straight impulse App. Meson Exchange Included Angular Dependence Experiment shows surplus yield at backward angles, and low energy
MORE RPA J.Nieves, I. Ruiz and M.J. Vincente Vacas arXiv: 1102.2777 [hep-ph] MiniBooNE SciBooNE
arXiv:1104.0125 Scaling Function, Spectral Function and Nucleon Momentum Distribution in Nuclei A.N. Antonov, M.V. Ivanov, J.A. Caballero, M.B. Barbaro, J.M. Udias, E. Moya de Guerra, T.W. Donnelly Scaling Function, Spectral Function and Nucleon Momentum Distribution in NucleiA.N. Antonov, M.V. Ivanov, J.A. Caballero, M.B. Barbaro, J.M. Udias, E. Moya de Guerra, arXiv:1103.0636 Relativistic descriptions of quasielastic charged-current neutrino-nucleus scattering: application to scaling and superscaling ideas Andrea Meucci, J.A. Caballero, C. Giusti, Andrea Meucci, J.A. Caballero, C. Giusti, J.M. Udias OTHER INTERESTING APPROACHES: Relativistic Potentials-FSI
Can the CCQE Cross Section/N Exceed the Free N Cross Section? J. Carlson et al, PR C65, 024002 (2002) Returning to the scaling of e-N QE cross section Scaling variable Scaling function Longitudinal- Transverse
PR C65, 024002 (2002) Investigated the increased transverse response between 3 He and 4 He
Euclidian Response Functions: PR C, 65, 024002 (cont.) :Nuclear gs, E=E 0 calculated with realistic NN and NNN interactions H: True Hamiltonian with same interactions as above R T, L (|q|,ω): Standard response functions from experiment. τ: units (MeV) -1, determines the energy interval of the response function NOTE: The group doing these calculation are extremely successful in reproducing all the features of light nuclei; Masses, energy spectra, transition rates, etc. for A≤ 12. Is presented, removing the trivial kinetic energy dependence of the struck nucleon, and the Q 2 dependence of the nucleon FF
What are the EM Charge and Current Operators?? Covariant single nucleon vector current negecting relatvistic corrections Current Conservation requires: A 2-body current
Results of Calculation, for fixed q 4 He T Note: QE data stops here
E T (τ) Let’s Look more carefully SRC produce interactions requiring large values of ω. SRC + 2-body currents produce increased yield.
How Big are these Effects Relative to Free Nucleons? Sum Rule at fixed 3 momentum transfer q:
Further Info from PR C65 024002 Small effect of 2-body currents evaluated in the Fermi Gas:!!! Effect is due to n-p pairs
Some More Evidence Amaro, et al, PHYSICAL REVIEW C 82, 044601 (2010) Meson Exchange Diags.Correlation Diags. 56 Fe, q=0.55GeV/c One body RFG 2p-2h fin. sts. Meson exchange Correlation Electron Scattering
e+d inclusive scattering The d the rms charge radius is 2 fm. p F ≅ 50MeV/c Absolute Normalization of the Flux p p pnpn p’ p Spectator proton (p p ) spectrum With ω and E μ known, E ν is determined!! With q and ω known, y=(ω+2mω) 1/2 - q < O can be selected.
Conclusions Impulse approximation is inadequate to calculate ν-nucleus CCQE, correlations and 2-body currents must be included Experimentalists must carefully specify what they call QE. Determining the incident neutrino energy is a serious issue. Measured Cross Sections are essential- Flux determination absolutely necessary Need a good calculation of ν-d cross section (5%) More work, theory and experiment on e-N transverse response might be the most fruitful avenue to pursue. Differences between ν and ν cross sections(yields) should be better understood before large and expensive($1B) CP violation searches are undertaken. I’m particularly worried about different incident energies being extracted from the two processes.